Anticorrosion agents and compositions comprising the same



Patented Jan. 13, 1953 ANTICORROSION AGENTS AND COMPOSI- TIONS COMPRISING THE SAME Albert G. Rocchini, Springdale, Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Application November 30, 1948, Serial No. 62,790

Claims. 1

This invention relates to certain new anticorrosion agents, and to hydrocarbon oil compositions comprising such agents and adapted to protect ferrous and other metal surfaces to which they are applied from rusting and other types of corrosion. 1

As is well known, simple hydrocarbon oil films afford only limited protection to metal surfaces against rusting and other types of corrosion, and in general cannot be relied upon to provide such protection in the presence of moisture or even under conditions merely of high humidity. Consequently, it has become common practice to employ corrosion inhibitors or anti-corrosion agents as additives in oil compositions for the purpose of providing additional protection against rusting and corrosion. Suchadditives have been used in various types of lubricating compositions, such as machine oils, internal combustion engine and diesel lubricating oils, greases, etc., as well as in slushing oils and the like, and even in fuel oils such as diesel or boiler fuels. The anti-corrosion agents heretofore employed this manner, however, have not proved entirely satisfactory under present-day serviceconditions. Certain of such agents do not provide adequate protection against corrosion under extreme conditions of moisture, humidity, and temperature. Others, while being satisfactory for use in oil compositions which are employed in the presence of only relatively pure water or water vapor, do not provide protection against corrosion by salt water or other aqueous solutions. Others deleteriously afiect certain desirable properties of the compositions in which they are used, e. g. lubricating value, demulsibility, etc.

Accordingly, it is an object of the present invention to provide anti-corrosion agents which may be incorporated in hydrocarbon oil compositions without detracting from the desirable properties of the oil, and which effectively protect metal surfaces with which such compositions come in contact from rusting and corrosion under extreme conditions of service.

Another object is to provide anti-corrosion agents suitable for use as such in lubricating oil compositions which are employed in the presence of large quantities of moisture and moisture vapor, e. g. steam turbine lubricating oil compositions.

A further object is to provide anti-corrosio :agents suitable for use as such in oil compositions :adapted to protect metal surfaces from salt water corrosion.

A still further object is to provide oil compositions comprising a relatively small proportion of an anti-corrosion agent and having improved properties and rustand corrosionprevention.

Other objects will be apparent from thefollowing detailed description of the invention, and

various advantages not specifically referred to herein will occur to those skilled in the art upon employment of the invention in practice.

I have found that the above objects and attendant advantages may be realized by incorporating into mineral oil compositions as an anticorrosion additive a minor amount of a waterinsoluble amide or imide of a substituted succinic acid containing as asubstituent a radical selected from the group of alkylthio or arylthio radicals, which radicals may or may not contain non-reactive substituents, and a primary or secondary amine having only one primary or secondary amino group. More specifically, I have found that amides and imides of this class are particularly well adapted for use as an anticorrosion additive for mineral oils, since they effectively inhibit rusting and corrosion of metals under very drastic corrosion conditions, and at the same time do not adversely affect the lubricating properties of the oil. Mineral oil compositions containing such products as corrosion inhibitors are especially well adapted for use in the presence of relatively large quantities of water and water vapor, e. g., as steam turbine oils and the like.

The amides and imides may be made by any suitable method. They can be made efficiently by reacting a primary or secondary amine having only one primary or secondary amino group (i. e., having only one amino group containing an N-hydrogen atom) with an anhydride of one of the substituted succinic acids. Amines containing two or more primary or secondary amino groups are not employed because their use results in resinous high molecular weight polymers. The reaction between the primary or secondary amine and the anhydride usually takes place readily with the evolution of heat, but in some cases mild heating is desirable to start the reaction. Because of the exothermic nature of the reactiornit is usually preferable to add the amine to the substituted succinic acid in small increments so that the temperature does not rise uncontrollably. To insure adequacy of reaction the mixture should attain a temperature of about 250 F. or higher. If the exothermic heat of reaction is not sufiicient under the conditions of operation to raise the temperature to this point, the mixture should be heated. It appears that an amide is the product initially formed, particularly at the lower reaction temperatures, and when a primary amine is employed the resulting. amide may beconverted at least in part to the imide at more elevated temperatures. The reaction products may be referred to as amido reaction products as they may be composed of the amide or the imide; or mixtures of the'two. I prefer to employ about equi-molec plafquantities ,of the anhydride and the amine,

since entirely satisfactory products are obtained under these conditions. ,However, the amine may be used in excessso as to produce at-the lower reaction temperatures a product containing a substantial proportion of the di-amide.

The amides and imides employed in accordance with the present invention may also be prepared from the substituted succinic acids directly. Since at low temperature conditionsthe reaction product between an amine of-the above class and a substituted succinic acid is a salt, it is necessary in order to produce the amide 0r imide to mix the acid and the nitrogen compound at an elevated temperature, which should be at least 250 F., or to heat the mixture prepared-at a low temperature to such an elevated temperature. The elevated temperature should be maintained for a time suificient to cause the decomposition of a salt between the substituted succinic acid and the amine and the production of thecorresponding amide or imide. .It is important to insure that any salt formed is converted to the amideor imide as the salts are generally highly water-solubleand therefore unsuitable for use in the composition of the present invention.

The amides and imides that are adapted for use in the compositions of the invention, and prepared for example as described above, are relatively high-boiling, light-colored liquids of medium viscosity to darker-colored semi-liquids or soft resinous solids. They are sufiiciently soluble in mineral oils to act as very efiective corrosion inhibitors in mineral oil compositions. They are also soluble in such organic solvents as hexane, chloroform, and benzene.

It will be obvious to those-skilled in the art that within the general description of theamides and imides given above compounds of varying degrees of solubility in mineral oil are included. The amides or imides that are especially suitable for use in the present compositions are those which are soluble in the mineral oil that forms the base for the compositions in "an amount equal to at least 0.005 per cent by weight of .the oil at atmospheric temperatures. The preferred amides or imides are those which are derivatives of substituted succinic acids in which the substituent group is an alkylthio radical containing at least 4 carbon atoms. Moreover, in cases where an amine containing a relatively small number of carbon atoms is employed for the production of the amide or imide. the substituent of the succinic acid should contain a relatively large number of carbon atoms, for example 8 to 18 carbon atoms.

The terms (alkylthio) and (arylthio) are employed herein to designate the group R-S- wherein the free valence of the sulfur atom is attached directly to a carbon atom, and R represents an alkyl or aryl radical. Thus, the term (alkylthiol-succinic acids is intended to refer to su inic ac ds in w ch van B-. group is attached directly to an alpha carbon atom, and is not to be confused with the alkyl-thiosuccinic acids, which are alkyl-substituted succinic acids in which sulfur replaces an oxygen atom in the carboxyl group.

The .(alkylthio) and (arylthio) -succinic acids and acid anhydrides employed in preparing the new anti-corrosion agents may be prepared by condensing maleio acid or maleic anhydride with an alkyl or aryl mercaptan in accordance with known procedure. In commercial practice, a mixture of mercaptans, particularly mercaptans containing from 4 to 18 carbon atoms, is usually condensed with-maleic anhydride at moderate temperaturesunder the influence of various catalysts so thattheresulting roduct isa mixture of succinic 'anhydride compounds bearing ,alkylthio and arylthio substituents of diiferent chain length and number of carbon atoms. Such technical mixtures are entirely suitable for use in preparing the anti-corrosion agentemployed in practice of the present invention, and in fact are usually preferred by reason of their availability and economy. The free alkylthioor arylthio substituted succinic :acids areobtainedby hydrating the corresponding acid anhydrides or mixtures thereof.

,Any primary or secondary amine containing only one primary or secondary amino group may be reacted with the above-defined succinic acid derivatives to form the new anti-corrosion agents. As examples of such amine compounds there may be mentioned primary and secondary aliphatic amines, such as methylamine, ,diethylamine, ethanolamine, ,butylamine, octylamine, laurylamine, hexadecylamine, isopropylamine, etc; cycloaliphatic amines, such as cyclohexylamine, dicyolohexylamine, methylqyclohexylamine; aromati .samineshsuch .as-iauilin alp and betanaphthylamine, toluidine, wdiphenylamine, aminodiphenyLamino-phenol, diethylaniline, acetami andheterocy lic amines, such as amino-benzoth'iazole, amino-pyridine, amino-quinoline.

Any of the above or mixtures thereof, or various oxygen, halogen, nitrogen, sulfur, or phosphorus derivatives of these compounds may be reacted with the above-defined succinic acid derivatives to form the anti-corrosion agents employed in mineral oil compositions inaccordance with the invention.

The-oil compositions of the present invention may be of various types having special properties adapting them for certain particular applications. Thus, they may be lubricating oil compositions ranging from light machine and household oils to heavy lubricants for large internal combustion engines, including diesel engines. Alternatively, they may be of the nature of protective oils or greasessuch as slushing oils or gun greases, or they may be adapted for use as cutting oils and the like. They are particularly well suited for use as steam turbine oils since they provide adequate protection against rusting and corrosion in the presence of relatively large quantities of water and Water vapor. They, may also be fuel oil compositions, including diesel engine fuel and domestic burner oils, whereby the anti-corrosion agent protects the tanks in which such oil is stored against corrosion brought about by the water with which such ,oils are often contaminated, as for example in the case of marine fuel oils which usually are contaminated with salt water giving rise to serious corrosionin the storage bunkers.

Regardless of the particular type of composition or thespecific use to which it is adapted, the new compositions of the invention are prepared simply by mixing the anti-corrosion agent with thedesiredhydrocarbon oil base to form a homogeneous composition. These agents function independently of other common oil additives, e. g., anti-oxidants, detergents, bearing corrosion inhibitors, viscosity index improvers, demulsifying agents, anti-foam agents, pour point depressants, etc, and accordingly may be used in conjunction with other such additives. They may be employed in varying amounts depending upon the severity of the corrosion conditions under which the compositions Will be used. Ordinarily, however, lubricatinscompositlonswill contain, less thangone "per cent; usually between about 0.01 and about 0.5 per cent, of the anti-corrosion agent, based on the weight of the base oil, whereas slushing oil type compositions may contain up to 10 or more per cent by weight of the corrosion inhibitor to provide adequate protection against corrosion under very drastic climatic conditions.

In testing and demonstrating the efficiency of the new anti-corrosion agents and mineral oil compositions comprising them, use is made of the so-called ASTM Corrosion Test. This test is that specified in the ASTM Standards on Petroleum Products and Lubricants, September 1945, and is designated as ASTM D,665-44T. In brief, this test consists in placing a 300 m1. sample of the oil composition comprising the anti-corrosion agent and 10 ml. of distilled water in a 400 ml. glass beaker which is immersed in a constant temperature bath maintained at 140 F. The beaker is fitted with a cover provided with openings for a stainless steel motor-driven stirrer and for insertion of a standard steel test bar, /g inch in diameter and 5 /2 inches long, which has been very carefully cleaned and polished just prior to the test. The stirrer is started, and when the oil sample in the beaker reaches a steady temperature of 1 l F..the test bar is inserted in the proper opening and hangs suspended from the beaker cover. Stirring is continued for 48 hours, after which the test bar is removed and examined for rust spots. The presence of any rust spots on the bar indicates failure to pass the test. A modification of this test, termed the Salt Water Corrosion Test, consists in the substitution of artificial sea water for the distilled water. The artificial sea water employed has the following composition:

NaCl 25.0 parts by weight MgCl-SI-IzO 11.0 parts by weight NazSOr 4.0 parts by weight CaClz 1.2 parts by weight Distilled water 1000.0 parts by weight The following examples will illustrate. a number of ways in which the principle of the invention has been applied, but are not to be construed as limiting the same. In all cases the base oil employed was a refined mineral lubricating oil having the following specifications:

Gravity, API 31.5-33.5

Viscosity, at 100 F., SUV 145-15 5 Viscosity, at 210 F., SUV 43 minimum Viscosity Index 107 Color s 1.0-1.5

Flash point, "F 400 Fire point, F 450 Example I (Octylthio)-succinic acid was prepared by heating an equi-molecular mixture of maleic acid and octyl mercaptan at a temperature of 50-90 C. for 6 hours. The reaction was carried out in dioxane solution employing a small quantity of ferrous chloride monohydrate as a catalyst. Upon completion of the reaction the crude product was poured into water and the crystalline solid which was thus precipitated was dissolved in benzene, treated with activated charcoal, and allowed to crystallize from the benzene solution. The (octylthio)-succinic acid product so obtained was a white crystalline solid having a melting point of about 95.5-9'7 C. Approximately 26 parts by weight of this product were mixed with approximately 24 parts'by weight of hexadecylamine. Reaction occurred spontaneously with the evolution of heat, "but toinsure complete reaction the mixture was heated to about 250 F. and maintained at this temperature for about 5 minutes. The reaction product obtained was a hard yellow wax-like product. A composition consisting of 1 part by weight of this product and 2000 parts by weight of the abovedescribed base oil successfully passed the hereinbefore-described ASTM Corrosion Test. The base oil itself failed to pass this test.

Example 11 Example II (Butylthio)succinic acid was obtained as a white crystalline solid melting at about 103.5 104 C. by reacting maleic acid with butyl mercaptan as in Example I. The product of reaction between this compound and hexadecylam'ine was a white wax-like solid. An oil composition containing 0.05 per cent :by weight of this product dissolved in the base oil passed the ASTM Corrosion Test.

Example IV The product of reaction between approximately equal parts by weight of (phenylthio)--succinic acid and hexadecylamine at 250 F. for about 5 minutes, was obtained as a semi-hard white solid. A composition consisting of 0.05 per cent by weight of this product dissolved in the base oil successfully passed the ASTM Corrosion Test.

Example V (Octadecylthi-o)-succinic anhydride was obtained by reacting maleic anhydride with octadecyl mercaptan. Approximately 39 parts by weight of the compound were then mixed and heated with approximately 24 parts by weight of hexadecylamine in 250 F. for about 5 minutes, whereby there was obtained a white waxy solid. This product was dissolved in the base oil'in an amount representing 0.05 per cent by weight to obtain an oil composition which successfully passed the ASTM Corrosion Test.

Example VI Approximately 41 parts by weight of (octa decylthiohsuccinic acid and approximately 9.9 parts by weight of aniline were mixed together, and maintained "at a temperature of about. 250? F. for about 5 minutes, wherebyreaction took place readily. The product of the reaction was ahard resinous solid having .a. light brown coloii lh composition consisting of 0.05 per cent by weight of this product dissolved in the base oil passed both the ASTM and Salt Water Corrosion Tests.

Example VI'I A mixture of equi-molecular' proportions of (octadecylthio)-succinic acid and cy'clohexylamine was heated to a temperature of about 250 F. for about 5' minutes, whereby reaction tools place to form a hard amberresin-like reaction product. A composition consisting; of 0.05. per,

. 7 cent by weight of thismroductdissolved in the base oil passed looth the ASTM and Salt Water Corrosion Tests.

Example VIII A hard yellow wax-like material was obtained as the product of reaction between (octadecylthlo) -succinic acid 'and amylamine at about 250 F. for about 5 minutes. An oil composition containing 0.05 per cent by weight of this product dissolved in the base oil passed both the ASTM and Salt Water Corrosion Tests.

- This application is a continuation-in-part of my co-pendin'g application, Serial No. 735,257, filed March .17., 1947, now abandoned.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the ingredients or method employed, providing the composition stated by-any of the following claims bepbtained.

I, therefore,'particularly point out claim as my invention:

1. An improved hydrocarbon oil composition comprising a major amount of a hydrocarbon oil and a minor amount of a nitrogen-containing compound selected from the group consisting of the amides and imides of substituted succinic acids having a substituent in the aliphatic chain,

selected from the group consisting of the alkylthio and a minor amount of a nitrogen-containing compound selected from the group consisting of the amides and imides of substituted succinic acids having as a substituent in the aliphatic 'chain an alkylthio radical containing at least four carbon atoms and an organic amine having only one amino group containing an N-hydrogen atom, the amount of said nitrogen-containing compound beingsufiicient to impart corrosioninhibiting properties to said composition.

.3. An improved mineral oil composition comprising a major amount of a mineral oil and a minor amount of a nitrogen-containing cs1. pound selected from the group consisting of the amides and imides of a substituted succinic acid having a substituent in the aliphatic chain, selected from the group consisting of the all' lthio and arylthio radicals, and an aliphatic amine having only one amino group containing an N-hydrogen atom, the amount of said nitrogen-containing compound being sufiicient to impart corrosion-inhibiting properties to said composition.

4. An improved mineral oil composition comprising a major amount of a mineral oil and a minor amount of a nitrogen-containing compound selected from the group consisting of the amides and imides of a substituted succinic acid having a substituent in the aliphatic chain, selected from the group consisting of alkylthio and arylthio radicals, and a cycloaliphatic amine having only one amino group containing an N- hydrogen atom, the amount of said nitrogencontaining compound being suihcient t impart corrosion-inhibiting properties to said composition. p

5, An. improved mineral oil composition comprising a major amount of a mineral oil and a minor amount oi a nitrogen-containing compound selected from the group consisting of the amides and imides of a substituted succinic acid having a substituent in the aliphatic chain, selected from the group consisting of the alkylthio and arylthio radicals, and a cyclohexylamine having only one amino group containing an N- hydrogen atom, the amount of said nitrogencontaining compound being sufficient to impart corrosion-inhibiting properties to said composition.

6. An improved mineral oil composition comprising a major amount of a mineral oil and a minor amount of a nitrogen-containing compound selected from the group consisting of the amides and imides of a'substituted succinic acid having a substituent in th aliphatic chain, selected from the group consisting of the all-:ylthio and aryithio radicals, and an aromatic amino having only one amino group containing an N-hydrogenatom, the amount of nitrogen-containing compound being sufficient to impart corrosion-inhibiting properties to said com position.

7. The composition of claim 6, wherein the aromatic amine is aniline.

8. An improved mineral oil composition comprising a major amount of a mineral oil and a minor amount of a nitrogen-containing compound selected from the group consisting of the inides and imides of a substituted succinic acid having as a substituent in the aliphatic chain an alkylthi'o radical containing four to eighteen carbon atoms and a cyclohexylamine having only one amino group containing an N-hydrcgen atom, the amount of said nitrogen-containing compound being sufiicient to impart corrosioninhibiting properties to said composition.

9. An improved mineral oil composition comprising a major amount of a mineral oil and a minor amount of a nitrogen-containing compound selected from the group consisting of the amides and imides of a substituted succinic acid having a substituent in the aliphatic chain, selected from the group consisting of alkylthio and arylthio radicals, and hexadecylamine, the amount of said nitrogen-containing compou d being sufficient to impart corrosion-inhibiting properties to said composition.

10. An improved mineral oil composition comprising a major amount of a mineral oil and a minor amount of a nitrogen-containing compound'selected from the group consisting of the amides and .imides of a substituted succinic acid having as a substituent in the aliphatic chain an alkylthio radical containing 4 to 18 carbon atoms and hexadecylamine, the amount or" said nitrogen-containing compound being SllfilClEIlt to impart corrosion-inhibiting properties to said composition.

ALBERT G. ROCCHINI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,182,173 Pinkernelle Dec. 5, 1939 2,279,560 Dietrich .Apr. 14, 1942 2,364,122 Bayes Dec. 5, 13cc 2,387,501 Dietrich Oct. 23, 1.945

OTHER REFERENCES Elleser eta-1., J. Am, Chem. Soc.--vcl. G9--pagci-3 2335-2333, 'OCtObEl' 1947. 

1. AN IMPROVED HYDROCARBON OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF A HYDROCARBON OIL AND A MINOR AMOUNT OF A NITROGEN-CONTAINING COMPOUND SELECTED FROM THE GROUP CONSISTING OF THE AMIDES AND IMIDES OF SUBSTITUTED SUCCINIC ACIDS HAVING A SUBSTITUENT IN THE ALIPHATIC CHAIN, SELECTED FROM THE GROUP CONSISTING OF THE ALKYLTHIO AND ARYLTHIO RADICALS, AND AN ORGANIC AMINE HAVING ONLY ONE AMINO GROUP CONTAINING AN NHYDROGEN ATOMS, THE AMOUNT OF SAID NITROGENCONTAINING COMPOUND BEING SUFFICIENT TO IMPART CORROSION-INHIBITING PROPERTIES TO SAID COMPOSITION. 